This invention relates in general to firearms, and in particular to rimfire rifles.
A rimfire rifle is so called because it fires rimfire cartridges. A rimfire cartridge has priming compound disposed around the inside rim of the cartridge casing base, the priming compound igniting the powder charge and causing discharge when the bottom of the cartridge is struck.
The popular rimfire calibers are known as follows: .22 Winchester Magnum Rimfire (.22 wmrf); .17 Hornady Rimfire Magnum (.17 hrm); .22 Long Rifle (.22 lr); and .17 Hornady Mach 2 (.17 hm2). The lengths and diameters of the cartridge casings for the .22 wmrf and .17 hrm calibers (referred to herein as “magnum calibers”) are the same. Consequently, rifles that shoot these calibers can utilize the same bolt and the same magazine, but they require different barrels. The .22 lr and .17 hm2 calibers (referred to herein as “small calibers”) are based on the same shorter cartridge casing. Rifles that shoot these calibers can utilize the same bolt and the same magazine, but the bolt and magazine for the 22 lr and .17 hm2 calibers is different than the bolt and magazine for the 22 wmrf and .17 hrm calibers. The .22 wmrf and .22 lr calibers have in common the diameter of the bullet, which is approximately 0.220 (inch). The cartridge casings for the 22 wmrf and .22 lr calibers being different in length and diameter, their respective barrels are different because of the differences in the chamber dimensions. [The chamber is the portion at the rear of the barrel (hereinafter “the barrel shank”) which is bored or reamed open to accept the cartridge.] The .17 hrm and .17 m2 calibers also have in common the diameter of the bullet, which is approximately 0.170, but they also require different barrels due to differences in chamber dimensions.
Known semi-automatic rimfire rifles are not designed to shoot different rimfire calibers. Although certain rifle designs can be converted to shoot other calibers, this requires gunsmithing work as they are not designed to do this. Previously a shooter who wished to shoot different caliber rimfire ammunition would have to purchase a different rifle for each caliber.
There is a need for a semi-automatic rifle design that would allow the shooter to purchase only one rifle that he/she may reconfigure to shoot cartridges (e.g., rimfire cartridges) of the caliber of his/her choice. This would result in a tremendous financial saving to the shooter and allow shooters a degree of flexibility previously unavailable.